Fuel injection apparatus for a two-stroke internal combustion engine

ABSTRACT

A fuel injection apparatus of the invention for a two-stroke engine including a fuel injection with an adjusting device, which via a pulsating pressure line is supplied with the pulsating internal pressure and inner chamber of a crankcase of the two-stroke engine, so as to meter the supply quantity of the fuel injection pump as a function of the internal pressure in such a way that exhaust emissions and fuel consumption of the two-stroke engine are reduced by means of a supply quantity optimally adapted to the combustion. The fuel injection apparatus according to the invention is intended for use in two-stroke engines.

BACKGROUND OF THE INVENTION

The invention is based on a fuel injection apparatus for a two-strokeinternal combustion engine.

A fuel injection apparatus for a two-stroke internal combustion engineis already known (offprint from MTZ, Motortechnische Zeitschrift[Automotive Engineering Journal], 13th year, No. 10, Oct. 1952), inwhich a fuel injection pump pumps fuel to a fuel injection valve thatinjects fuel directly into a combustion chamber of the two-strokeengine. The fuel injection pump is embodied as a so-called in-line pump,in which each cylinder of the two-stroke engine is supplied with fuelvia a separate pump element. The pump element is composed of a pumppiston and a pump cylinder. The pump piston is guided longitudinallydisplaceably in the pump cylinder and is driven via a drive element by acamshaft of the two-stroke engine. For controlling the performance ofthe two-stroke engine, a throttle valve rotatably supported in athrottle valve neck is actuated; to that a rod linkage is provided onthe throttle valve, the linkage being connected to a gas pedal or a gaslever. In operation of the two-stroke engine, a certain negativepressure is established in the throttle valve neck; this pressuredepends on the rotary position of the throttle valve, so that it can beutilized to regulate the supply quantity of the fuel injection pump. Inthis prior art, the negative pressure is drawn off downstream of thethrottle valve and carried via a pulsating pressure line to an adjustingdevice. The adjusting device is part of the fuel injection pump, and asa function of the negative pressure prevailing in the throttle valveneck it regulates the supply quantity of the fuel injection pump. Tovary the supply quantity, the pump piston is rotated, and includes aface which has a recess on its outer jacket in the form of an obliquelyextending control edge. By means of the control edge, the pump pistoncontrols a control bore that is in the pump cylinder and discharges intoa pump work chamber of the pump piston; the rotary position of thecontrol edge relative to the control bore determines the end of pumpingby the pump piston. The useful stroke and thus the supply quantity arevaries by means of the location of the pump piston in the pump cylinder.

For rotating the pump piston, a sleevelike control element is provided,the interior of which has an opening with two longitudinal slits; aslaving device embodied on the pump piston, for instance in the form ofa piston lug, glides axially displaceably on the longitudinal slits andengages them, so as to rotate the pump piston only when a rotation ofthe control element occurs. For its actuation, the control element has atoothed segment, which for instance is clamped onto its outer surfaceand with which a control rod, accommodated crosswise to a longitudinalaxis of the pump piston in the housing of the fuel injection pump,meshes with outer teeth, so as to cause a rotation of the controlelement and pump piston upon a longitudinal displacement of the controlrod. In the prior art in question, the control rod is mounted by one endon a diaphragm of an adjusting device, which as a function of thenegative pressure in the throttle valve neck determines the supplyquantity of the fuel injection pump. To that end, the diaphragm of theadjusting device divides two pressure chambers from one another inpressure-tight fashion, that is, a connection pressure chamber and anadjusting pressure chamber, so that if there is a pressure differencebetween the connection pressure chamber and the adjusting pressurechamber, the diaphragm is moved in the direction of the pressure drop.As the diaphragm moves, the control rod mounted on the diaphragm isdisplaced, and at the same time the control element is rotated in orderto effect an adjustment of the supply quantity of the fuel injectionpump. In this prior art, the adjusting pressure chamber is acted upon byambient pressure and the connection pressure chamber is acted upon bynegative pressure of the throttle valve neck, so that depending on thepressure difference present at the diaphragm, a displacement of thecontrol rod and via the control element a rotation of the pump pistontakes place.

In regulating the performance of the two-stroke engine as described bymeans of a negative pressure in the throttle valve neck, however, it ispossible only at extremely inconvenience to adapt the supply quantity tovarying operating parameters of the two-stroke engine. Doing so requiresadditional devices. For instance, the influence of the ambient pressure,which decreases with increasing geodetic altitude and thus a decreasingair fill in the cylinders of the two-stroke engine, can be ascertainedonly by means of an additional altitude pressure sensor. The influenceof the temperature of the air aspirated by the two-stroke engine canalso be detected only by means of a temperature sensor that beingconnected with the fuel injection pumps suitably adapts the supplyquantity to the air temperature. Typically, the temperature sensor isaccommodated outside the fuel injection pump in the throttle valve neck.The temperature sensor is connected by means of a rod linkage to thefuel injection pump control rod, in order to actuate it in compensatingfashion as a function of the temperature of the aspirated air, so thatan adaptation of the supply quantity to variable aspirated airtemperatures takes place.

Advantages of the Invention

The fuel injection apparatus according to the invention has theadvantage over the prior art that in a simple way, an adaptation of thesupply quantity of the fuel injection pump to varying operatingparameters of the two-stroke engine is accomplished; in particular, theproportions of polluting exhaust gas components and fuel consumption ofthe two-stroke engine drop markedly.

By means of the provisions recited herein, advantageous further featuresof and improvements to the fuel injection apparatus disclosed arepossible. Advantageously, a starter device that can be turned on uponcold starting of the two-stroke engine makes a further reduction inpolluting exhaust gas components possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in simplified form inthe drawing and are explained in further detail in the ensuingdescription. FIG. 1 is a schematic function diagram of a fuel injectionapparatus according to the invention; FIG. 2 is a section through a fuelinjection pump of a first exemplary embodiment of the invention; FIG. 3is a section through the fuel injection pump taken along a line 3--3 ofFIG. 2; and FIG. 4 is a section through the fuel injection pump inaccordance with a second exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a schematic function diagram of a fuel injection apparatus1 according to the invention, in which a fuel injection pump 2 isprovided for supplying fuel to a two-stroke internal combustion engine 4shown in fragmentary form in section. The fuel injection pump 2 pumpsfuel to a fuel injection valve 3, provided on a cylinder 5 of thetwo-stroke engine 4, that injects the fuel directly into a combustionchamber 12 of the two-stroke engine 4. In the process, via an intaketube 9, the two-stroke engine 4 aspirates the requisite air forcombustion into an inner chamber 10 of a crankcase 11 of the two-strokeengine, from which the air flows, via overflow conduits not shown infurther detail, into the combustion chamber 12 under the control of apiston 6 accommodated in displaceable fashion in the cylinder 5. Theexhaust gases produced in combustion are removed from the combustionchamber 12 via an outlet conduit 14. By way of example, the two-strokeengine 4 is intended for driving hand-held power tools, such as powerchainsaws, cutting-off grinders, shrub trimmers, and for driving mopeds,motorboats, and lawnmowers or the like. A fuel prefeed pump 15 furnishesfuel to the fuel injection pump 2 and is composed of a low-pressure pumppart 17 and an intake buffer 18 preceding the low-pressure pump part 17,as shown inside a dashed lines in FIG. 1. The fuel prefeed pump 15 isdriven by the internal pressure in the crankcase 11 of the two-strokeengine 4, which pulsates in the inner chamber 10 of the crankcase 11; tothat end, a pressure line 26 is provided, which leads to the innerchamber 10 of the crankcase 11 from a work chamber 25, defined by adiaphragm 24, of the low-pressure pump part 17. The diaphragm 24, via atappet 27, controls a pump diaphragm 28 that defines a pump chamber 29.The pump chamber 29 communicates via an intake valve 30 with a fuelinlet 31 that carries the fuel from a fuel tank 32. Via a pressure line33 and a low-pressure line 34, the fuel is carried in the direction ofthe arrows 39 to a low-pressure connection 35 of the fuel injection pump2; excess fuel pumped from the low-pressure pump part 17 flows back in aprovided fuel return line 37, in the direction of the arrows 40, via areturn valve 36 from the fuel injection pump 2 to the fuel tank 32.

The fuel injection pump 2 and the fuel injection valve 3 correspond intheir basic design to known Diesel technology. Since the fuel is nolonger introduced into the combustion chamber 12 via an otherwisetypical carburetor into the intake tube 9 in the form of a fuel-airmixture mixed with oil but instead is injected directly into thecombustion chamber 12 and therefore no longer comes into contact with aninner wall 41 of a cylinder of the two-stroke engine 4, a lubricant oilpump 42 is necessary. The lubricant oil pump 42 pumps oil to thecrankshaft bearing, connecting rod bearing, and piston pin boss, and inparticular to the inner wall 41 of the cylinder. By way of example, thelubricant oil pump 42 is driven by a crankshaft 43 of the two-strokeengine 4, which is shown in dashed lines in FIG. 1 and via a connectingrod 44 converts the up-and-down motion of the piston 6 into a rotarymotion of the crankshaft 43. For pumping the oil, the lubricant oil pump42 has a feed screw, which has bevel gearing, for instance, on its end.The bevel gearing meshes with spur gearing provided on the crankshaft43, in order to pump the oil out of an oil tank 45 and oil filters 46,provided by way of example, via a pressure valve 47 by means of the feedscrew.

In the exemplary embodiments, the fuel injection pump 2 is embodied as aso-called plug-in injection pump. As shown in FIG. 2, one pump piston 55and one pump cylinder 56 form a single pump element, which feeds thefuel to the two-stroke engine 4, which is embodied for instance with asingle cylinder. It is also possible for the fuel injection pump to beof the so-called in-line pump type, in which a single pump element isprovided for each cylinder, and the pump elements are disposed in line,i.e. one after the other, in a common housing. As shown in FIG. 1, thefuel injection pump 2 is driven in a known manner by a cam 53 mounted onthe crankshaft 43, via a drive element 50 of the fuel injection 2. Asshown in FIG. 2, the drive element 50 is composed of a tappet 51, whichis longitudinally displaceable in a sleeve 61 and which via a springplate 52 and a piston spring 54 is pressed against the cam 53 of thecrankshaft 43, in order by the eccentric shape of the cam 53 to move thetappet 51 up and down. It is also possible by the shaping of the cam 53to adjust the duration of fuel injection, the performance and speed ofpumping of the fuel injection pump 2.

The tappet 51 drives the pump piston 55 in order to feed fuel via a feedline 60 to the fuel injection valve 3. To that end, the pump piston 55is accommodated longitudinally displaceably in the pump cylinder 56along a longitudinal axis 67 extending centrally through the pump piston55, and with an end face 57 located in the pump cylinder 56 it definespump work chamber 58 in the pump cylinder 56. The pump piston 55 isfitted into the pump cylinder 56 with the utmost precision, so that evenat high pressures and low rpm of the two-stroke engine 4, the pumppiston 55 remains tight, and no further seal is needed. On its lowerend, the pump piston 55 is held freely rotatably on the tappet 51 via aheadpiece 62; the piston spring 54, via the spring plate 52 retained onthe pump cylinder 56, engages a head plate 59 in the region of itsheadpiece 52, so that the piston spring 54 is tensed in the workingstroke of the pump piston 55. After the working stroke, the pistonspring 54 returns the pump piston to its outset position; the pistonspring 54 presses the tappet 51 permanently against the cam 53, so thatthe tappet does not lift away from or hop off the cam 53.

A control bore 65 and an outlet bore 66 discharge into the pump workchamber 58; these bores are made in the pump cylinder 56 and are alignedwith one another along a control axis 75 that is oriented crosswise tothe longitudinal axis 67. The pump cylinder 56 and the inner pump piston55 are accommodated in a housing 70 of the fuel injection pump 2. Fromthe low-pressure pump part 17 shown in FIG. 1, pumped fuel flows via thelow-pressure connection 35 to the pump piston 55 shown in FIG. 2, intoan annular chamber 69 located between the housing 70 and the pumpcylinder 56 and from that chamber to the control bore 65. By way ofexample, the outlet bore 66 likewise communicates with the annularchamber 69 and the control bore 65, so that the fuel diverted uponpumping of the pump piston 55 can be fed, for example via an outletconnection on the housing 70, which connection is not identified byreference numeral but communicates with the outlet bore 66, into thefuel return line 37, in which the fuel flows back to the fuel tank 32.For diverting the fuel, the pump piston 55 has a bore 71, which is madecentrally in the pump piston 55, and a control edge 73 recessed from ajacket face 72 of the pump piston 55. The control edge 73 is partiallyvisible in FIG. 2 and is embodied by way of example as a so-calledtop-located control edge 73. The bore 71 extends from the end face 57 inthe direction of the tappet 51, for example parallel to the longitudinalaxis 67, as far as the control edge 73, which extends obliquely to thelongitudinal axis 67.

The design and mode of operation of a fuel injection pump 2, operatingwith a pump piston 55 having a control edge 73 and control bore 65, isknown to one skilled in the art of Diesel technology and will thereforebe described only briefly below. The fuel flowing into the pump workchamber 58 via the control bore 65 is compressed by the pump piston 55on its upward motion; a pressure valve 85 defining the pump work chamber58 remains initially closed in the process. A compression spring 87 ofthe pressure valve 85 acts upon a valve closing body 86, embodied forinstance as a ball, so that a connection 76 from the pump work chamber58 to a feed bore 63, provided in a feed portion 77 of the fuelinjection pump 2, is closed. After the onset of pumping by the pumppiston 55, the valve closing member 86 opens, at a pressure that can bespecified by the compression spring 87, and thus fuel from the pump workchamber 58 reaches the connection 76 and flows past the pressure valve85 into the feed bore 63. Next, the fuel from the feed bore 63 flowsinto the feed line 60 connected to the feed bore 63 to the fuelinjection valve 3.

The supply quantity of the fuel injection pump 2 can be adjusted bymeans of the rotary position of the control edge 73 of the pump piston55 relative to the outlet bore 66; in a known manner, the control edge73 controls the timing of the end of pumping of the fuel that has flowedinto the pump work chamber 58 via the control bore 65, so that thepumping stroke of the pump piston 55 and thus the supply quantity can beadjusted by rotation of the pump piston 55, or in other words of thecontrol edge 73. In the exemplary embodiment, the fuel injection pump 2pumps fuel at a pressure of approximately 35 bar into the feed line 60to the fuel injection valve 3.

For rotating the pump piston 55, a rotatable control element 80 isemployed, which by way of example is embodied as a control sleevepartially surrounding the pump piston 55. The control element 80 ispressed against the pump cylinder 56 by the piston spring 54 and thespring plate 52. The connection of the control element 80 to the pumppiston 55 is embodied such that an axial displaceability of the pumppiston 55 is possible at all times, while conversely upon a rotation ofthe control element 80, a rotation of the pump piston 55 also ensues. Tothat end, two longitudinal slits, for example, are machined out of aninner wall of the control element 80, and in them a piston slavingdevice 74, a so-called piston lug, is guided axially slidingly; upon arotation, it engages the longitudinal slits of the control element 80 inorder to bring about a corresponding rotation of the pump piston 55.

As shown in FIG. 3, which is the sectional view along a line 3--3 ofFIG. 2, the control element 80 on its outer face 81 has an engagementgroove 83, which extends into the plane of the drawing of FIG. 3 and forexample extends at least partway in the direction of the longitudinalaxis 67. The engagement groove 83 is engaged by an engagement body 84,which is connected to a control rod 82. The control rod 82 extendswithin the interior of the housing 70 of the fuel injection pump 2,offset from the control element 80, along a transverse axis 68 thatextends crosswise to the longitudinal axis 67. By way of example, theengagement body 84 is embodied as a ball head or a pin, and it protrudesfrom an outer face 88 of the control rod 82. The engagement body 84engages the engagement groove 83 of the control element 80, so as tocause a rotation of the control element 80 and the pump piston 55 upon adisplacement of the control rod 82.

The control rod 82 is supported in the interior of the housing 70 of thefuel injection pump 2 by means of two bearings 91, 92, for instanceslide bearings. In terms of the view of FIG. 3, the control rod 82 issecured by its left-hand end 93 to a diaphragm 94 of an adjusting device90. The diaphragm 94 divides two pressure chambers from one another inpressure tight fashion. In the ensuing description, the pressure chambershown on the left of the diaphragm 94 in FIG. 3 will be called theconnection pressure chamber 96, and the pressure chamber shown on theright of the diaphragm 94 in FIG. 3 will be called the adjustingpressure chamber 97. The connection pressure chamber 96 communicates viaa pulsating pressure connection 99 with a pulsating pressure line 100.By a connection not shown in FIG. 3, the adjusting pressure chamber 97communicates for instance with the atmosphere, for instance via anopening 101 provided in the adjusting pressure chamber 97 and via afilter 102, provided at the opening 101, in the housing 70. As shown inthe exemplary embodiment of FIG. 1, however, the opening 101 may alsocommunicate via a connection, not identified by reference numeral, witha starting pressure line 104 that leads to a starter device 105, whosetask and function will be described in further detail later in thedescription of the exemplary embodiment.

For joining the control rod 82 to the diaphragm 94, a connection piece106 is mounted to both sides of the diaphragm 94; the connection pieceis connected to an end piece, located in the adjusting pressure chamber97, of the control rod 82. On a side of the connection piece 106 towardthe control element 80, a pair 107 of bimetallic disks is provided whichencompasses an end region of the control rod 82 and is pressed againstthe connection piece 106 by a spring plate 108 by means of a compressionspring 109. The pair 107 of bimetallic disks is composed for instance oftwo joined-together metal disks which have different coefficients ofthermal expansion. When the metal disks heat up, they bend, so that thecompression spring 109 is compressed or in other words more heavilyloaded. The compression spring 109 is braced on one side of thediaphragm 94 by the connection piece 106, via the spring plate 108 andthe pair 107 of bimetallic disks, and on the opposite side is braced ona shoulder 103 via a support ring 110. The shoulder 103 is embodied inthe adjusting pressure chamber 97 in the region of the bearing 91 shownon the left in FIG. 3. The diaphragm 94 is acted upon by the compressionspring 109 in such a way that when the pressures in the connectionpressure chamber 96 and the adjusting pressure chamber 97 areapproximately equal, this spring rests, with the connection piece 106located in the connection pressure chamber 96, against an idlingadjusting screw 111 that protrudes into the connection pressure chamber96.

When pressure of the connection pressure chamber 96, which is higherthan the ambient pressure prevailing in the adjusting pressure chamber97, is exerted, the diaphragm 94 is moved to the right in terms of FIG.3, counter to the force of the compression spring 109, so that theconnection piece 106 located in the connection chamber 96, lifts awayfrom an end of the idling adjusting screw 111 protruding into theconnection pressure chamber 96. With the diaphragm 94 in motion, thecontrol rod 82 connected to the diaphragm 94 is shifted to the right;the engagement body 84 rotates the control element 80 counterclockwiseand rotates the pump piston 55 shown in FIG. 2, in order thereby toincrease the supply quantity of the fuel injection pump 2. If thepressure difference is negligible, the compression spring 109 displacesthe diaphragm 94 so that the control rod 82 reaches its outset positionagain and the connection piece 106 rests on the idling adjusting screw111. Screwing the idling adjusting screw 111 inward or outward thereforemakes it possible to adjust the minimum supply quantity of the fuelinjection pump 2, or to adjust the idling rpm of the two-stroke engine.

The second bearing 92 is accommodated in the housing 70 of the fuelinjection pump 2, on an end 95 shown on the right in FIG. 3 of thecontrol rod 82, and is retained by a screwable bearing sleeve 112. Tothat end, the bearing sleeve 112 has a male thread on its outer face sothat it can be screwed firmly to the housing into a female thread of thehousing 70 that extends from an end face 114 of the housing 70 in thedirection of the control element 80 past the bearing 92. In thescrewed-in state of the bearing sleeve 112, a closure piece 116 of thebearing piece 112 rests on the end face 114 of the housing 70; an axialclearance 118 remains between the end 95, shown on the right in FIG. 3,of the control rod 82 and an inner wall 117, toward the control rod 82,of the bearing sleeve 112. The axial clearance 118 is necessary toenable motion of the control rod 82 along the transverse axis 68.Protruding into the clearance 118 is an adjusting screw 119, screwedinto the thread of the closure piece 116 of the bearing bush 112; thisscrew is retained in a manner secure against relative rotation by a locknut 120 on the closure piece 116 of the bearing sleeve 112. Theadjusting screw 119 is provided in order to limit a maximum displacementof the control rod 82 in the direction of the transverse axis 68 thatoccurs upon maximum imposition of pressure in the connection pressurechamber 96. When maximum pressure is imposed in the connection pressurechamber 96, the control rod 82 is shifted to the right in terms of FIGS.3 and 4, until with an end face 98 on its right-hand end 95 the controlrod 82 meets the adjusting screw 119, so that by screwing the adjustingscrew 119 in or out, the maximum displaceable travel of the control rod82, the maximum rotation of the control rod 80 and thus a maximum supplyquantity of the fuel injection 2 can be established.

Heating up of the pair 107 of bimetallic disks shortens the fastenedlength of the compression spring 109, resulting in an increased springforce of the compression spring 109; hence a greater pressure differencebetween the overpressure in the connection pressure chamber 96 and theambient pressure in the adjusting pressure chamber 97 is necessary inorder to displace the control rod 82. If there is a rising temperaturein the connection pressure chamber 96, for instance from a temperatureincrease in the inner chamber 10 of the crankcase 11 (FIG. 1), or arising temperature in the adjusting pressure chamber 97, for instancefrom a rising ambient temperature, the pair 107 of bimetallic diskscauses a reduced displacement of the control rod 82, while the pressuredifference in the connection pressure chamber 96 and adjusting pressurechamber 97 remains constant, so that correspondingly less fuel is pumpedby the fuel injection pump 2 to the fuel injection valve 3.

The adjusting pressure chamber 97 shown in FIGS. 3 and 4 communicates inthe exemplary embodiment with the starter device 105 shown in FIG. 1 bymeans of a connection, not identified by reference numeral, on thehousing 70 of the fuel injection 2. The starter device 105 is connectedto the intake tube 9 downstream of a throttle valve 20 via a connectionpressure line 115. The throttle valve 20 serves in a known manner toregulate the performance of the engine 4 and is supported in the intaketube 9 so as to be pivotable about a shaft. The throttle valve 20 canfor instance be actuated by means of a rod linkage not identified byreference numeral that is connected for example to a gas pedal or a gaslever. The starter device 105 is turned on manually, for instance, onlyin the cold starting phase of the two-stroke engine 4, so as to carrythe negative pressure, established in the intake tube 9 in operation ofthe two-stroke engine 4, to the starter device 105 via the connectionpressure line 115 and from the starter device, via the starting pressureline 104, to the adjusting pressure chamber 97 of the adjusting device90. By means of the negative pressure that prevails instead of theambient pressure in the adjusting pressure chamber 97, there isconsequently a greater pressure difference between the overpressure andthe connection pressure chamber 96 and a negative pressure in theadjusting pressure chamber 97; as a result, the control rod 82 isdeflected more sharply, so that when the starter device 105 is actuated,the supply quantity of the fuel injection pump 2 is increased. After theheating of the two-stroke engine 4 that ensues in operation, the starterdevice 105 can be turned off again. When the starter device 105 isturned off, the starting pressure line 104 is switched to theatmosphere, so that ambient pressure is again established in theadjusting pressure chamber 97, which reduces the supply quantity of thefuel injection pump 2 after the cold starting phase.

As shown in FIG. 1, the pulsating pressure line 100 leads to a controlopening 125. The control opening 125 is recessed out of the inner wall41 of the cylinder 5. Corresponding with the control opening 125, apiston opening 127 is recessed out from a circumferential wall 126 ofthe piston 6 and communicates with the inner chamber 10 of the crankcase11. At a certain position of the piston 6 in the cylinder 5, the controlopening 125 and the piston opening 127 open into one another, so thatthe internal pressure in the inner chamber 10 of the crankcase 11 iscarried via the pulsating pressure line 100 to the connection pressurechamber 96 of the adjusting device 90. Since upon the outward motion inthe direction of top dead center (TDC), the piston 6 generates anegative pressure in the inner chamber 10 of the crankcase 11 that isnot meant to be carried to the connection pressure chamber 96, a valve128 is required, which cuts off the negative pressure portion of thepulsating internal pressure in the crankcase 11. The valve 128 isdisposed in the pulsating pressure line 100, for instance, and if thereis overpressure in the pulsating pressure line 100 it assumes an openposition, in the downward motion of the piston 6 toward bottom deadcenter (BDC), and otherwise this valve is closed. By a suitable choiceof the location of the control opening 125 in the cylinder 5, a certainrange of the internal pressure in the crankcase 11 can be chosen, suchas 15° to 60° before reaching bottom dead center (BDC) of the piston 6,and carried via the control opening 125 and the pulsation line 100 theconnection pressure chamber 96. The overpressure of the crankcase 11carried to the connection pressure chamber 96 is higher than the ambientpressure in the adjusting pressure chamber 97, so that the diaphragm 94of the adjusting device 90 is moved in the direction of the pressuredrop. The moving diaphragm 94 displaces the control rod 82, toward theright in terms of FIGS. 3 and 4, whereupon the control element 80 isrotated. By means of a throttle 129 connected parallel to the valve 128,the throttle for instance regulating the pressure in the pulsatingpressure line 100, and by means of a second throttle 130 connectedupstream of the valve 128, fine metering of the supply quantity of thefuel injection pump 2 can be carried out. Since only the pressuredifference between the overpressure in the crankcase 11 and the ambientpressure is used to control the supply quantity of the fuel injectionpump 2, the influence of a varying ambient pressure, for instance from achange in geodetic altitude, can be compensated for by a correspondingvariation in the supply quantity of the fuel injection pump 2. Thechoice of the location of the control opening 125 in the cylinder 5, orof the location of the correspondingly disposed piston opening 127, mustbe done in such a way that an internal pressure in the crankcase 11 thatcharacterizes wide operating ranges of the two-stroke engine 4 is found,at which internal pressure, because of the always optimally adaptedsupply quantity of the fuel injection pump 2, unobjectionable operationof the two-stroke engine 4 with optimal combustion and only slightexhaust emissions is possible. It has been demonstrated that this ispossible with a control opening 125 that is recessed out of the innerwall 41 of the cylinder approximately in the circumferential region ofthe intake tube 9. It is optimally also advantageous to provide aplurality of control openings at various locations on the inner wall 41of the cylinder, which by way of example are disposed along a commonline, so that they can be triggered by a common piston opening or by aplurality of piston openings. It is also conceivable to provide aplurality of control openings in the inner wall 41 of the cylinder thatcan be triggered some of them at the same time or in succession bycorrespondingly provided piston openings.

FIG. 4 shows a second exemplary embodiment according to the invention ofthe fuel injection apparatus 1 with the fuel injection pump 2; allelements that are the same or function the same are identified by thesame reference numerals as in FIGS. 1-3. Unlike the first exemplaryembodiment in FIG. 3, in FIG. 4 the compression spring 109 isaccommodated in the region of the right-hand end 95 of the control rod82. Without using the bearings 112 of the first exemplary embodiment,the right-hand bearing 92 is accommodated in a bearing recess 137provided in the housing 70. A spring plate 135 on which the compressionspring 109 is supported is connected to the right-hand end 95 of thecontrol rod 82. The compression spring 109 is accommodated in a steppedsleeve 132, which is screwed with a male thread into a female threadextending from the end face 114 of the housing 70 of the fuel injectionpump 2 as far as the right-hand bearing 92. The compression spring 109surrounds part of the adjusting screw 119 accommodated in the sleeve 132and is supported with a support ring 132 against the pair 107 ofbimetallic disks, which unlike the first exemplary embodiment isaccommodated in an inner chamber 136 formed by the sleeve 132 and by ascrew-in part 138 of the sleeve 132. The pair 107 of bimetallic springsis supported against the screw-in part 138, which by way of example isscrewed into the sleeve 132 by means of a female thread. The adjustingscrew 119 is likewise screwed into a female thread provided on thescrewed-in part 138 and is retained in a manner fixed against relativerotation by means of a lock nut 120. As in the first exemplaryembodiment, a clearance 118, which enables displacement of the controlrod 82, is present between the spring plate 135 and the adjusting screw119. The clearance 118 can be varied by screwing the adjusting screw 119in or out, so that the maximum displacement of the control rod 82 isadjustable by means of the adjusting screw 119.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A fuel injection apparatus for a two-stroke internalcombustion engine, comprising a fuel injection pump, said fuel infectionpump includes a pump piston driven via a drive element by a crankshaftaccommodated in a crankcase of the two-stroke engine and guidedlongitudinally in a pump cylinder, said pump piston includes an end facewhich defines a pump work chamber and a jacket face which has anobliquely extending control edge that controls the fuel pumped out ofthe pump work chamber to a fuel injection valve that injects the fueldirectly into a combustion chamber of the two-stroke engine, a controlelement connected to the pump piston, said control element controls asupply quantity of the fuel injection pump being effected by rotatingthe pump piston, the control element being actuatable by an adjustingdevice via a control rod accommodated in a housing of the fuel injectionpump and connected to the control element, the adjusting device includesa diaphragm which divides two pressure chambers from one another and towhich the control rod is connected, the adjusting device (90) is actedupon by the internal pressure prevailing in the crankcase (11) of thetwo-stroke engine (2).
 2. The fuel injection apparatus of claim 1, inwhich the adjusting device (90) can be connected via a pulsatingpressure line (100) to a control opening (125) of a cylinder (5) of thetwo-stroke engine (4), the opening being made in an inner wall (41) ofthe cylinder, which control opening, upon coincidence with a pistonopening (127) made in a circumferential wall (126) of a piston (6) ofthe two-stroke engine (4), the piston opening being open to thecrankcase (11), intermittently establishes a pressure connection withthe internal pressure in the crankcase (11).
 3. The fuel injectionapparatus of claim 2, in which in the pulsating pressure line (100), avalve (128) is provided which upon overpressure in the crankcase (11)opens toward the adjusting device (90).
 4. The fuel injection apparatusof claim 3, in which one or more throttles (129, 130) are disposed inthe pulsating pressure line (100).
 5. The fuel injection apparatus ofclaim 4, in which at least one of the throttles (129, 130) is embodiedas pressure-controllable.
 6. The fuel injection apparatus of claim 1, inwhich a compression spring (109) is provided in the adjusting device(90), its spring force being variable by a bimetallic element (107). 7.The fuel injection apparatus of claim 2, in which a pressure chamber(97) defined by the diaphragm (94) is connected via a pressureconnection (104, 115) to an intake tube (9) of the two-stroke engine(4).
 8. The fuel injection apparatus of claim 7, in which a starterdevice (105) is provided, which selectively makes a pressure connectionof the pressure chamber (97) with either the pressure in the intake tube(9) or the ambient pressure.